Cutting tool assemblies of this kind are known wherein the replaceable cutting insert is formed with a main body portion having at one or both ends thereof terminal cutting edges. The insert holder is formed with a pair of clamping jaws defining between them an insert receiving recess. The insert is designed to be located within the recess with the operative cutting edge projecting outwardly and with the clamping jaws effectively gripping the insert at its body portion. The cutting tool assembly can be of the wedge-clamping type wherein the body portion is wedge-shaped as is the insert receiving recess, so that the insert is effectively wedge-clamped between the clamping jaws. Alternatively, one of the clamping jaws can be articulated with respect to the insert holder and mechanical means such as, for example, screw clamping means, are employed so as effectively to clamp the insert body portion between the clamping jaws.
In all cases, the effective clamping of the cutting insert in the insert holder must ensure that the insert is effectively retained against displacement under the cutting forces, and that the relative positioning of the insert with respect to the insert holder is maintained substantially invariant, both during cutting operations and also when inserts have to be replaced.
For this purpose, and in particular to ensure that the lateral position of the insert vis-a-vis the insert holder is maintained invariant both during cutting operations and upon replacement of inserts, it is known to provide the respective surfaces of the insert and clamping jaws which come into clamping relationship with each other (hereinafter "the clamping surfaces") with respectively elongated mating ribs and recesses of respectively convex and concave cross-sectional shapes. In this way, and when the insert is inserted into the insert receiving recess, the mating of the ribs within the recesses effectively inhibits lateral displacement of the insert with respect to the insert holder.
Thus, it is known in this connnection to form the ribs and recesses with respectively V-shaped cross-sectional shapes or, alternatively, with smoothly curved, arcuate cross-sectional shapes. It is found in practice, however, that, as a result of production tolerances, it is practically impossible to ensure sufficiently close matching of the convex rib within the concave recess. Thus, if the concave recess has significantly lesser dimensions than the convex rib, it will be clearly difficult for the rib to mate effectively within the recess. If, on the other hand, the concave recess is of significantly larger dimensions than the convex rib, it will be difficult, if not impossible, to ensure unique lateral positioning of the insert within the holder.
This problem is particularly aggravated in view of the fact that the cutting insert to be held within the holder is of very much harder material than that of the holder, and therefore the clamping surfaces of the clamping jaws tend to become rapidly worn, and this contributes to the difficulties in ensuring unique lateral dispositioning of the insert within the holder.
Whilst the difficulties referred to above occur with cutting tool assemblies used, for example, in parting operations wherein the cutting forces are radially directed with respect to the workpiece and are therefore directed along the longitudinal axis of the cutting insert, the difficulties become particularly acute where the cutting tool assembly is used also for laterally directed cutting operations such as, for example, turning and wherein the cutting insert is therefore subjected to laterally directed forces tending to displace the cutting insert in a lateral direction.